Processing method and processing device

Abstract

To provide a wafer processing method capable of processing a wafer in a short time, with high precision, or at low cost.SOLUTION: In a processing method, a grinding wheel facing the outer peripheral region of a wafer is brought into contact with a wafer contained in an area surrounded by the grinding wheel in a planar view, and the grinding wheel cuts into the wafer in the thickness direction to grind and remove the outer peripheral region.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a wafer processing method and processing apparatus. [Background technology]

[0002] With the recent trend toward miniaturization of electronic devices, semiconductor wafers on which multiple devices are formed are required to be ground thinner. When ultra-thinning a wafer, a process is performed to remove the peripheral region in advance to prevent edge chipping from occurring in the peripheral region and wafer cracking that may result from edge chipping. This process is sometimes called edge trimming.

[0003] Edge trimming is an important process that contributes to wafer thinning and improved yield, and it is important to select the optimal method depending on the wafer material, size, required device specifications, etc. For example, edge trimming must be compatible with wafers made of a variety of materials, such as LiNBO3 (lithium niobate) / silicon, sapphire / silicon, quartz glass / silicon, LiTaO3 (lithium tantalate) / silicon, / sapphire, and LiTaO3 / quartz.

[0004] In addition, there is an increasing demand for micro-sensors used in driving automobiles and surface acoustic wave filter devices for communication in smartphones, and to manufacture these devices, functional bonded wafers are produced that bond different types of wafers, such as oxides, dielectrics, and optical materials, as well as bonded wafers that bond multiple wafers together for higher integration.

[0005] Edge trimming of bonded wafers mainly includes a method of processing the outer edge (edge) of the wafer W from the front surface before bonding (pre-bonding edge trimming), and a method of fully cutting the outer edge of the wafer W from the back surface after bonding (post-bonding edge trimming).

[0006] In the pre-bonding edge trimming, the outer peripheral edge of the wafer is trimmed from the front surface side of the wafer by a predetermined amount, for example, about 150 μm to 200 μm.

[0007] In edge trimming after bonding, the outer peripheral edge of the wafer needs to be fully cut, and the amount of cutting of the outer peripheral edge of the wafer may be approximately the same as the original thickness of the wafer W. Edge trimming after bonding may require more cutting force than edge trimming before bonding. Therefore, in edge trimming after bonding, taking into consideration the processing load, the outer peripheral edge of the wafer is cut using, for example, a blade with a coarse grain size and a processing speed set to a slow speed.

[0008] Conventionally, edge trimming has been known to eliminate device defects and the like by partially removing the chamfered portion on the periphery with a cutting blade. Patent Document 1 describes a method in which the wafer and cutting blade are rotated, the cutting blade rotating at high speed is caused to cut a predetermined depth at one point, and the wafer is cut along the outer periphery of the wafer to remove the edge surface.

[0009] In order to improve throughput by processing in a short time, it is known to form a modified layer inside the wafer using a high-frequency laser, and then remove the peripheral portion of the wafer using the modified layer as a starting point during grinding, as described in Patent Document 2.

[0010] Patent Document 3 also describes a method of lowering a rough grinding wheel while rotating it, and rubbing the outer periphery of the semiconductor substrate with the outside of the rough grinding wheel to chamfer the outer periphery of the semiconductor substrate. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-217461 [Patent Document 2] Patent No. 7109537 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-038267 Summary of the Invention [Problem to be solved by the invention]

[0012] The technique described in Patent Document 1 requires a long processing time to obtain the desired shape due to factors such as wear on the cutting blade, load on the wafer, and a narrow contact area between the wafer and the grindstone.

[0013] The method described in Patent Document 2 requires a high frequency laser device and the associated laser head, modified layer forming device, and processing unit, which increases the initial cost.

[0014] The present disclosure solves at least one of the problems of the conventional techniques. Specifically, the present disclosure provides a wafer processing method that can process wafers in a short time, with high accuracy, or at low cost. The present disclosure also provides a processing apparatus. [Means for solving the problem]

[0015] The first processing method of the present disclosure is a processing method in which a grinding wheel facing the outer peripheral region of a wafer is brought into contact with the wafer contained in an area surrounded by the grinding wheel in a planar view, and the grinding wheel cuts into the wafer in the thickness direction to grind it and remove the outer peripheral region.

[0016] The second processing method of the present disclosure is a processing method in which, in the first processing method, the grinding wheel is brought into contact with the wafer parallel to the surface of the wafer and the grinding wheel cuts into the wafer in the thickness direction to grind it.

[0017] A third processing method of the present disclosure is the first processing method, wherein the grinding wheel has an outer diameter larger than the diameter of the wafer, an inner diameter smaller than the diameter, and the grinding wheel is positioned relative to the wafer so that the central axis of the grinding wheel and the central axis of the wafer coincide.

[0018] The fourth processing method of the present disclosure is a processing method in which, in the first processing method, the inner diameter of the grinding wheel is larger than the diameter of the wafer, and the grinding wheel is cut into the wafer in the thickness direction to grind it so that only a portion of the grinding wheel contacts the outer peripheral region.

[0019] A fifth processing method of the present disclosure is the first processing method, wherein the grindstone has at least one notch in the circumferential direction.

[0020] A sixth processing method of the present disclosure is the first processing method, wherein the contact and grinding are carried out by at least the following steps: bringing the grinding wheel close to the wafer from the direction facing the surface; cutting in the thickness direction at a first speed when the grinding wheel contacts the surface; and switching the cutting speed to a second speed after cutting a predetermined amount at the first speed, wherein the second speed is greater than the first speed.

[0021] A seventh processing method of the present disclosure is the first processing method, wherein the grinding is performed by separating the grindstone and the wafer periodically or non-periodically.

[0022] An eighth processing method of the present disclosure is the seventh processing method, wherein the spacing is performed by applying ultrasonic vibration to at least one of the grindstone and the wafer.

[0023] A ninth processing method of the present disclosure is the first processing method, wherein the grinding stone has a concentric multi-layer structure.

[0024] A tenth processing method of the present disclosure is the ninth processing method, wherein each layer constituting the multilayer structure is brought into contact with the other layer independently to form cuts with different cross-sectional shapes in the wafer.

[0025] The processing apparatus disclosed herein is a processing apparatus that removes an outer peripheral region from a wafer, and is equipped with a holder that holds the wafer, a grinding wheel that faces the outer peripheral region of the wafer, and a rotation mechanism that rotates at least one selected from the group consisting of the grinding wheel and the wafer in a circumferential direction, and the wafer is contained in an area surrounded by the grinding wheel when viewed in a plane. [Effects of the Invention]

[0026] According to the present disclosure, there is provided a wafer processing method that can process wafers in a short time, with high accuracy, or at low cost. The present disclosure also provides a processing apparatus. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a partial cross-sectional view schematically showing a processing device of a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 3] 3 is a partial cross-sectional view schematically showing an example of edge trimming by the processing device according to the first embodiment. FIG. [Figure 4] FIG. 4 is a partial cross-sectional view schematically illustrating an example of a processing device at the end of edge trimming according to the first embodiment. [Figure 5] 3 is a partial cross-sectional view schematically showing an example of edge trimming of a bonded wafer by the processing apparatus according to the first embodiment. FIG. [Figure 6] 3 is a partial cross-sectional view schematically showing an example of edge trimming of a bonded wafer by the processing apparatus according to the first embodiment. FIG. [Figure 7] 1 is a partial cross-sectional view schematically illustrating an example of the processing apparatus 100 at the end of edge trimming on the bonded wafer according to the first embodiment. FIG. [Figure 8] 4 is a flowchart of edge trimming by the processing device according to the first embodiment. [Figure 9] 10 is a flowchart of edge trimming by a processing device according to a modified example of the embodiment. [Figure 10] FIG. 10 is a partial cross-sectional view schematically showing an example of edge trimming by the processing device according to the second embodiment. [Figure 11] FIG. 11 is a cross-sectional view taken along line BB in FIG. [Figure 12] FIG. 10 is a partial cross-sectional view schematically showing a processing device according to a third embodiment. [Figure 13] FIG. 10 is a partial cross-sectional view schematically showing an example of grinding by an outer grindstone of the processing device according to the third embodiment. [Figure 14] FIG. 11 is a partial cross-sectional view schematically showing an example of a processing device at the end of grinding by an outer grindstone according to a third embodiment. [Figure 15] FIG. 11 is a partial cross-sectional view schematically illustrating an example of a processing device according to a third embodiment at the start of grinding by an inner grindstone of the processing device. [Figure 16] FIG. 11 is a partial cross-sectional view schematically showing an example of grinding by an inner grindstone of the processing device according to the third embodiment. [Figure 17] FIG. 11 is a partial cross-sectional view schematically illustrating an example of a processing device at the end of grinding by an inner grindstone according to a third embodiment. [Figure 18] 10 is a flowchart of edge trimming by the processing device according to the third embodiment. [Figure 19] 10A and 10B are a partial cross-sectional view and a bottom view schematically showing a processing apparatus 400 according to a fourth embodiment. [Figure 20] 10 is a flowchart of edge trimming by a processing apparatus 400 according to a fourth embodiment. [Figure 21] 10A and 10B are a partial cross-sectional view and a bottom view schematically showing a processing apparatus 400 according to a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0028] The processing device and the processing method will be described in detail below with reference to the drawings. (Embodiment 1) FIG. 1 is a partial cross-sectional view schematically illustrating a processing apparatus 100 according to a first embodiment. FIG. 1 illustrates an X direction, a Y direction, and a Z direction. The X direction intersects with the Y direction, and the Z direction intersects with the X and Y directions. For example, the X direction is perpendicular to the Y direction, and the Z direction is perpendicular to the X and Y directions. Hereinafter, in the Z direction, the tip side of the arrow in FIG. 1 may be referred to as the top (upper side or upward direction), and the opposite direction to the top may be referred to as the bottom (lower side or downward direction). Furthermore, the thickness direction of a workpiece (a wafer W, described later), for example, the Z direction in FIG. 1, may be referred to as the thickness direction.

[0029] The processing apparatus 100 is, for example, a grinding apparatus. The processing apparatus 100 grinds a plate-shaped body (hereinafter, sometimes referred to as a workpiece). For example, the processing apparatus 100 edge-trims the chamfered portion of the outer periphery of the excess area surrounding the device area where the device of the workpiece is formed, the outer periphery area, or the end (hereinafter, sometimes referred to as a trimming area). Hereinafter, the term "edge trimming" is used to mean removing part or all of the end of a material, or removing and trimming it. Note that the processing apparatus 100 may be an apparatus other than a grinding apparatus, or may be an apparatus called an edge-trimming apparatus.

[0030] The workpiece includes a wafer W, and is formed from, for example, sapphire, SiC (silicon carbide), GaN (gallium nitride), lithium tantalate, or other compound semiconductor or oxide material. Note that the workpiece may also be formed from materials other than these. Hereinafter, the term "wafer" may also be used to mean "a single ordinary wafer" and / or "a bonded wafer formed by bonding multiple wafers together."

[0031] The processing apparatus 100 includes, for example, a grinding wheel 1, a flange 2, a spindle 3, a suction table (or suction chuck) 4, a chuck spindle 5, a motor 6, a table motor (chuck motor) 7, a grinding wheel 10, and a controller (controller) 90. Note that the processing apparatus 100 may include components other than the grinding wheel 1, the flange 2, the spindle 3, the suction table (or suction chuck) 4, the chuck spindle 5, the motor 6, the table motor 7, the grinding wheel 10, and the controller (controller) 90.

[0032] The controller (control unit) 90 controls each part of the processing device 100, such as the grinding wheel 1, flange 2, spindle 3, suction table (or suction chuck) 4, chuck spindle 5, motor 6, table motor 7, grinding wheel 10, etc.

[0033] In the example shown in FIG. 1, the grinding wheel 1 is detachably attached to the flange 2. The grinding wheel 1 has a grinding wheel 10 on the lower side opposite to the upper side that is detachably attached to the flange 2. The grinding wheel 1 is formed, for example, in an annular shape. The grinding wheel 1 rotates via the flange 2 when a motor 6 is driven.

[0034] The flange 2 is attached to the spindle 3. The flange 2 is formed, for example, in a disk shape.

[0035] The grinding wheel spindle 3 is provided so as to be movable up and down by a spindle feed mechanism (not shown) or the like. The grinding wheel spindle 3 is also connected to a motor 6. In the example shown in FIG. 1, the motor 6 is shown as being directly connected to the grinding wheel spindle 3, but it may be connected to the grinding wheel spindle 3 via another member, for example, a belt or the like.

[0036] The suction table 4 holds the wafer W by suction. The suction table 4 is connected to a table motor 7 via a chuck spindle 5. In the example shown in FIG. 1, the table motor 7 is shown as being directly connected to the chuck spindle 5, but it may be connected to the chuck spindle 5 via another member, for example, a belt. The suction table 4 is rotated by being driven by the table motor 7. In the example shown in FIG. 1, the grinding wheel 1 (flange 2 and grinding spindle 3) is shown as rotating in the opposite direction to the wafer W (suction table 4), but they may rotate in the same direction.

[0037] FIG. 2 is a cross-sectional view taken along line AA in FIG.

[0038] As shown in FIG. 2, the area surrounded by the grinding stone 10 or grinding wheel 1 (or flange 2) overlaps the entire surface of the wafer W in a plan view. In other words, the area surrounded by the grinding stone 10 or grinding wheel 1 (or flange 2) accommodates the wafer W in a plan view. Note that the area surrounded by the grinding stone 10 or grinding wheel 1 (or flange 2) does not have to overlap the entire surface of the wafer W in a plan view, as long as most of the area of ​​the wafer W overlaps. In other words, the area surrounded by the grinding stone 10 or grinding wheel 1 (or flange 2) accommodates most of the area of ​​the wafer W.

[0039] The grinding wheel 10 is provided along the shape of the grinding wheel 1, for example, in an annular shape. A radially inner portion of the grinding wheel 10 (hereinafter sometimes referred to as the inner portion of the grinding wheel 10) or a radially part of the grinding wheel 10 (hereinafter sometimes referred to as a part of the grinding wheel 10) overlaps the outer peripheral edge of the wafer W over the entire circumference of the outer peripheral edge of the wafer W. In the example shown in FIG. 2, the inner portion of the grinding wheel 10 (or a part of the grinding wheel 10) overlaps the trimming region of the outer peripheral edge of the wafer W over the entire circumference of the outer peripheral edge of the wafer W. Note that the inner portion of the grinding wheel 10 may overlap the trimming region of the wafer W over a portion of the outer peripheral edge of the wafer W. Furthermore, the grinding wheel 10 may overlap the entire circumference or a part of the outer peripheral edge of the wafer W or the trimming region of the wafer W.

[0040] For example, in a plan view, the radial width of the outer peripheral region of the wafer W where the grinding wheel 10 overlaps (hereinafter, sometimes simply referred to as the width of the outer peripheral region) is approximately uniform over the entire circumference of the outer peripheral region of the wafer W. Note that, in a plan view, the width of the outer peripheral region of the wafer W where the grinding wheel 10 overlaps may differ at each position on the outer peripheral region of the wafer W.

[0041] The grinding stones 10 are segmented, that is, divided into a plurality of pieces, in the circumferential direction of the grinding wheel 1. The grinding stones 10 have a notch (or gap) 11 between two adjacent grinding stones.

[0042] Since the grinding wheel 10 comes into contact with the surface of the wafer W during processing of the wafer W, the inside may become sealed, but the formation of the notch 11 allows for the introduction / exhaust of coolant and the discharge of grinding chips, etc.

[0043] FIG. 3 is a partial cross-sectional view that schematically shows an example of edge trimming by the processing apparatus 100 according to this embodiment. The wafer W is placed on the suction table 4 and held by vacuum. The wafer W is disposed so as to face the grinding wheel 10.

[0044] The grinding wheel 10 faces the outer periphery of the wafer W. In the example shown in FIG. 3, an inner portion of the grinding wheel 10 (or a part of the grinding wheel 10) faces the trimming region of the wafer W. The entire radial direction of the grinding wheel 10 may face the trimming region of the wafer W. That is, the contact portion between the grinding wheel 10 and the wafer W is adjusted to have the width of the trimming region to be removed. The lower surface of the grinding wheel 10 is preferably formed in a flat shape substantially parallel to the surface of the wafer W. The lower surface of the grinding wheel 10 does not have to be substantially parallel to the wafer W and may be inclined. The grinding wheel 10 (grinding wheel 1 and / or flange 2) may be inclined with respect to the surface of the wafer W.

[0045] The outer diameter of the grinding wheel 10 is slightly larger than the outer diameter of the wafer W. The inner diameter of the grinding wheel 10 is approximately the same as the end face diameter of the edge-trimmed wafer W. In the example shown in FIG. 3, the outer diameter of the grinding wheel 10 is slightly larger than the outer diameter of the wafer W, and the inner diameter of the grinding wheel 10 is slightly smaller than the outer diameter of the wafer W. The outer diameter of the grinding wheel 10 may be equal to or larger than the outer diameter of the wafer W, or may be smaller than the outer diameter of the wafer W. The inner diameter of the grinding wheel 10 may be equal to or larger than the outer diameter of the wafer W, or may be smaller than the outer diameter of the wafer W.

[0046] The suction table 4 is rotated around the rotation axis Ow of the suction table 4 via the chuck spindle 5 by driving the table motor 7. In other words, the wafer W is rotated around the rotation axis Ow via the suction table 4. Furthermore, the grinding wheel 1 and the flange 2 are rotated around the rotation axis Ot of the grinding wheel 1 (or grinding wheel 10) via the grinding wheel spindle 3 by driving the motor 6. In other words, the grinding wheel 10 is rotated around the rotation axis Ot via the grinding wheel 1 and the flange 2. Note that in the example shown in FIG. 3, both the grinding wheel 10 and the suction table 4 (wafer W) are rotating, but it is sufficient if at least one of the grinding wheel 10 and the suction table 4 (wafer W) is rotating.

[0047] 3, the rotation axis (or central axis) Ot of the grinding wheel 10 (grinding wheel 1, flange 2, and / or grinding wheel spindle 3) and the rotation axis (or central axis) Ow of the wafer W (suction table 4 and / or chuck spindle 5) coincide or approximately coincide. Note that the rotation axis of the grinding wheel 10 (grinding wheel 1, flange 2, and / or grinding wheel spindle 3) and the rotation axis of the wafer W (suction table 4 and / or chuck spindle 5) do not have to coincide (they may be misaligned).

[0048] For example, the position (or arrangement) of the suction table 4 (or wafer W) and / or grinding wheel 10 (grinding wheel 1, flange 2, and / or grinding wheel spindle 3) may be adjusted by the controller 90 or the like so that the rotation axis Ow of the wafer W and the rotation axis Ot of the grinding wheel 10 (grinding wheel 1, flange 2, and / or grinding wheel spindle 3) approximately coincide (are approximately coaxial). Note that if the positions of the suction table 4 (or wafer W) and grinding wheel 10 (grinding wheel 1, flange 2, and / or grinding wheel spindle 3) are uniquely determined, there is no need to adjust these positions.

[0049] As shown in Fig. 3, the grinding stone 10 (grinding wheel 1 and flange 2) descends in the Z direction from above the wafer W toward the surface (upper surface) of the wafer W (descending in the direction of the arrow in Fig. 3), cutting into and grinding the trimming region of the wafer W (edge ​​trimming). By grinding the grinding stone 10 in this manner while facing the entire circumference or part of the trimming region of the wafer W, it is possible to cut into and grind (edge ​​trim) the entire circumference or part of the trimming region of the wafer W substantially simultaneously or at one time.

[0050] The positioning of the grinding wheel 10 and the wafer W may be adjusted based on the groove shape of the wafer W that is ground by bringing the grinding wheel 10 into contact with the wafer W. Alternatively, the grinding wheel 10 and the wafer W may be positioned by the controller 90 or the like based on data obtained by grinding a member having the same shape as the wafer W in advance and acquiring data on the groove shape of the ground member.

[0051] The grinding wheel 10 is, for example, a metal bond with a mesh size of approximately #400 to #800, and is adjusted taking into consideration the lifespan and processing quality of the grinding wheel 10. The rotation speed of the grinding wheel spindle 3 is, for example, 1000 to 4000 rpm. The rotation speed of the chuck spindle 5 is, for example, 500 to 2000 rpm. The cutting speed, which is the feed speed of the grinding wheel 10 and grinding wheel 1, is, for example, 0.1 to 5 mm / sec. Each of these parameters can be appropriately selected depending on the material of the workpiece, etc.

[0052] The coolant (grinding fluid) is discharged toward the processing point where the grinding wheel 10 and the wafer W come into contact. The coolant flows between the segments (notches 11) of the grinding wheel 10 and into the inside of the grinding wheel 10, cooling the processing point and discharging grinding debris and wear particles (broken and fallen abrasive grains) of the grinding wheel 10. This can improve the processability of the wafer W by the grinding wheel 10.

[0053] The grinding wheel 10 (the grinding wheel 1 and the flange 2) descends from a predetermined position, for example, an initial position, toward the wafer W at a predetermined descending speed, decelerates just before abutting (or contacting) the wafer W, and cuts into the wafer W at a cutting speed (first speed) that is smaller than the cutting speed (second speed) at which a groove is formed in the wafer W when the grinding wheel 10 abuts against the wafer W. The grinding wheel 10 then cuts into the wafer W at a cutting speed (second speed) that is larger than the first speed when the groove begins to form in the wafer W. When the grinding wheel 10 abuts against the wafer W and starts processing (grinding), a large force may be applied to the edge (edge) of the wafer W. Therefore, by performing processing at the first speed, which is smaller than the second speed, at the start of grinding, edge chipping can be suppressed. When grinding the wafer W, the grinding wheel 10 preferably contacts the wafer W approximately parallel to the surface of the wafer. The descending speed and cutting speed of the grinding wheel 10 can be controlled by a controller (controller) 90.

[0054] Furthermore, the grinding wheel 10 (the grinding wheel 1 and the flange 2) may be lowered from a predetermined position, for example, an initial position, toward the wafer W at a predetermined lowering speed, and may contact and cut into the wafer W. The grinding wheel 10 may periodically or aperiodically contact and cut into the wafer W to grind it. For example, the grinding wheel 10 may repeatedly perform the following operation: descend, contact the wafer W, and cut into it for a predetermined period of time, then rise a predetermined amount to separate from the wafer W, and then descend again to contact the wafer W and cut into it for a predetermined period of time. This operation may be controlled by a controller (control unit) 90. Repeatedly performing the operation of cutting into the wafer W, grinding it, and then separating from the wafer W can facilitate the discharge of grinding debris and the like.

[0055] FIG. 4 is a partial cross-sectional view schematically illustrating an example of the processing apparatus 100 at the end of edge trimming according to this embodiment. When a predetermined amount of the trimming area of ​​the wafer W has been removed by the grinding wheel 10, the processing apparatus 100 ends edge trimming. When edge trimming ends, the grinding wheel 10 (the grinding wheel 1 and / or the flange 2) moves upward from the wafer W in the Z direction (toward the tip of the arrow in FIG. 4) as shown in FIG. 4, and returns to a predetermined position, for example, the initial position.

[0056] Hereinafter, the edge trimming of the bonded wafer W according to this embodiment will be described with reference to FIGS. 5 to 7. However, since the contents are almost the same as those described above with reference to FIGS. 1 to 4 except that the wafer W is a bonded wafer W, the differences will mainly be described.

[0057] FIG. 5 is a partial cross-sectional view schematically showing an example of edge trimming of a bonded wafer W by the processing apparatus 100 according to this embodiment. The bonded wafer W has an upper substrate 20 which is the bonded device side, an intermediate layer 21 which is an adhesive layer, and a lower substrate 22. The upper substrate 20 and the lower substrate 22 are bonded together via the intermediate layer 21. In the example shown in FIG. 4, the lower substrate 22 is placed on the suction table 4. The intermediate layer 21 is placed on the lower substrate 22. The upper substrate 20 is placed on the intermediate layer 21.

[0058] The suction table 4 suction-holds the bonded wafer W. The suction table 4 (bonded wafer W) is rotated by driving a table motor 7. In the example shown in FIG. 4, the grinding wheel 1 (flange 2 and grinding wheel spindle 3) is shown rotating in the opposite direction to the bonded wafer W (suction table 4), but they may rotate in the same direction.

[0059] FIG. 6 is a partial cross-sectional view schematically showing an example of edge trimming of a bonded wafer W by the processing apparatus 100 according to this embodiment. 6 cuts into and grinds the trimming region of the bonded wafer W, similar to the grinding wheel 10 shown in Fig. 3. In the example shown in Fig. 6, the grinding wheel 10 cuts into and grinds from the upper substrate 20 to a part of the lower substrate 22 in the Z direction, forming a terrace (step portion) at the edge of the wafer W.

[0060] For example, the grindstone 10 removes (edge ​​trims) the upper substrate 20, the intermediate layer 21, and the lower substrate 22 substantially simultaneously in a single cutting operation. When the upper substrate 20 is made of a material with relatively low material strength and the intermediate layer 21 is formed of an oxide film or the like (insulating layer) and has relatively low bonding strength, edge trimming, in which the upper substrate 20, the intermediate layer 21, and the lower substrate 22 are removed substantially simultaneously in a single cutting operation, is suitable. In addition to the above, edge trimming, which removes the upper substrate 20, intermediate layer 21, and lower substrate 22 approximately simultaneously in a single cutting operation, is also suitable when the finished thickness of the upper substrate 20 is thin (Si thin film processing, GaAS thin film deposition), when the upper substrate 20 is formed in the N phase, the intermediate layer 21 is formed in an insulating layer, and the lower substrate 22 is formed in the P phase (e.g., Si-on-Si), and the device characteristics are two or three phases, or when the upper substrate 20 is made of a highly brittle material that causes cracks or chips in the upper substrate 20 and intermediate layer 21 when thinned.

[0061] FIG. 7 is a partial cross-sectional view schematically showing an example of the processing apparatus 100 at the end of edge trimming on the bonded wafer according to this embodiment. The processing apparatus 100 ends edge trimming when a predetermined amount of the trimming region of the bonded wafer W has been removed by the grindstone 10. When edge trimming is completed, the grindstone 10 (the grindstone wheel 1 and / or the flange 2) moves upward from the bonded wafer W in the Z direction (toward the tip of the arrow in FIG. 7) as shown in FIG. 7, and returns to a predetermined position, for example, the initial position.

[0062] FIG. 8 is a flowchart of edge trimming by the processing apparatus 100 according to this embodiment. The controller 90 adjusts at least one of the positions of the grinding wheel 10 and the wafer W (suction table 4) (S10). For example, the controller 90 adjusts at least one of the positions of the grinding wheel 10 and the wafer W (suction table 4) so ​​that the rotation axis Out of the grinding wheel 10 and the rotation axis Out of the wafer W substantially coincide with each other (become coaxial).

[0063] The controller 90 rotates the grinding wheel 10 and the wafer W (suction table 4), and lowers the grinding wheel 10 to bring the grinding wheel 10 into contact with the wafer W (S11). For example, the controller 90 rotates the grinding wheel 10 and the wafer W, lowers the grinding wheel 10, and decelerates it just before it comes into contact with the wafer W to bring the grinding wheel 10 into contact with the wafer W.

[0064] When the grinding wheel 10 comes into contact with the wafer W, the controller 90 cuts into the wafer W by a predetermined amount in the thickness direction at a first cutting speed to grind it (S12). The cutting amount cut into the wafer W at the first speed is not particularly limited, but is preferably within a range of 0.0001 to 0.5 when a target cutting amount (hereinafter sometimes referred to as target cutting amount) for edge trimming the wafer W (in its trimming region) is 1.

[0065] When the controller 90 determines that the wafer W has been cut a predetermined amount in the thickness direction at the first speed, it switches the cutting speed from the first speed to a second speed and cuts and grinds the wafer W in the thickness direction at the second speed to the target cutting amount (S13).

[0066] Fig. 9 is a flowchart of edge trimming by the processing apparatus 100 according to a modified example of this embodiment. In Fig. 9, S10 and S11 are the same as in Fig. 8, and therefore description thereof will be omitted.

[0067] The controller 90 cuts into the wafer W in the thickness direction and grinds it (S20). The controller 90 repeatedly executes the operation of grinding the wafer W for a predetermined time in the thickness direction and separating it from the wafer W until the target cutting depth is reached (S21). For example, the controller 90 periodically or non-periodically executes the operation of grinding the wafer W and separating it from the wafer W.

[0068] According to this embodiment and its modified examples, the grinding wheel 10 contacts the trimming region over the entire circumference or a portion of the wafer W at approximately the same time, and cuts into the trimming region over the entire circumference or a portion of the wafer W by small amounts at approximately the same time to grind (edge ​​trim) the wafer. The grinding wheel 10 also rotates around a rotation axis Ot that is approximately coaxial with the rotation axis Ow of the wafer W, and descends in the Z direction to cut into and grind the trimming region of the wafer W. In other words, when processing the wafer W, the grinding wheel 10 can process the wafer W only by moving in a direction perpendicular to the surface of the wafer W, and does not involve movement in a horizontal direction relative to the surface of the wafer W. Therefore, it is not necessary to consider the effect on processing of the accuracy of the horizontal movement relative to the surface of the wafer W. Therefore, by increasing the processing speed of the grinding wheel 10, for example, the rotation speed of the grinding wheel 10, the cutting speed of the grinding wheel 10, the rotation speed of the wafer W (adsorption table 4), or a combination thereof, not only can the wafer W be processed in a short time, but the shape accuracy of the wafer W after processing, particularly the quality of the cross-sectional shape, can be improved.

[0069] Hereinafter, the first embodiment and its modifications, as well as other embodiments and modifications, will be described. In the other embodiments and modifications, the same components as those in the first embodiment and its modifications will be given the same reference numerals, and detailed descriptions thereof will be omitted. (Embodiment 2) The processing apparatus 200 according to the second embodiment differs from the processing apparatus 100 according to the first embodiment in part of the configuration and the edge trimming method.

[0070] FIG. 10 is a partial cross-sectional view schematically showing an example of edge trimming by the processing apparatus 200 according to the second embodiment. The processing device 200 includes, for example, a grinding wheel 1, a flange 2, a spindle 3, a suction table (or suction chuck) 4, a chuck spindle 5, a motor 6, a table motor (chuck motor) 7, a grinding wheel 10, a controller (controller) 90, and a nozzle NZ. Note that the processing device 200 may include components other than the grinding wheel 1, the flange 2, the spindle 3, the table (or chuck) 4, the chuck spindle 5, the motor 6, the table motor 7, the grinding wheel 10, the controller (controller) 90, and the nozzle NZ.

[0071] The grinding wheel 10 is provided so that a part of it faces a part of the outer peripheral edge of the wafer W. In the example shown in Fig. 10, an inner part of a grinding wheel 10A (or a part of the grinding wheel 10A) in the circumferential direction of the grinding wheel 10 is provided so as to face a part of the outer peripheral edge of the wafer W.

[0072] 10, the outer diameter of the grinding wheel 10 is larger than the outer diameter of the wafer W. However, as long as the grinding wheel 10 is provided so as to come into contact with a portion of the wafer W, the outer diameter of the grinding wheel 10 may be equal to or smaller than the outer diameter of the wafer W.

[0073] 10, the grinding wheel 10 and the wafer W rotate in the same direction. However, the grinding wheel 10 and the wafer W may rotate in opposite directions.

[0074] 10, the rotation axis Ot of the grinding wheel 10 and the rotation axis Ow of the wafer W (suction table 4) are eccentric. For example, the rotation axis Ot of the grinding wheel 10 and the rotation axis Ow of the wafer W (suction table 4) are misaligned in the X direction. In other words, the grinding wheel 10 (grinding wheel 1, flange 2, and / or grinding wheel spindle 3) and the wafer W (suction table 4, and / or chuck spindle 5) are arranged eccentrically.

[0075] For example, the positions of the suction table 4 and / or grinding wheel 10 may be adjusted by the controller 90 or the like so that the grinding wheel 10A faces (or can come into contact with) the trimming region of the wafer W. For example, the controller 90 adjusts (or moves) the positions of the suction table 4 (or wafer W) and grinding wheel 10 in the X and / or Y directions based on the distance between the rotation axis Ow and the rotation axis Ot, the difference between the outer diameter of the grinding wheel 10 and the diameter of the wafer W, and the inner diameter of the grinding wheel 10 and the diameter of the wafer W, thereby causing the grinding wheel 10A to face the trimming region of the wafer W. Note that if the positions of the suction table 4 and grinding wheel 10 are uniquely determined, these positions do not need to be adjusted.

[0076] FIG. 11 is a cross-sectional view taken along line BB in FIG. As shown in Fig. 11, the area surrounded by the grinding stone 10 or grinding wheel 1 (or the flange 2) overlaps the entire surface of the wafer W in a plan view (or accommodates the wafer W). Note that the area surrounded by the grinding stone 10 or grinding wheel 1 (or the flange 2) does not have to overlap the entire surface of the wafer W in a plan view, as long as most of the area of ​​the wafer W overlaps. In other words, the area surrounded by the grinding stone 10 or grinding wheel 1 (or the flange 2) accommodates most of the area of ​​the wafer W.

[0077] The grinding wheel 10A is a part of the grinding wheel 10 that overlaps a portion of the outer periphery of the wafer W. In the example shown in FIG. 11, the grinding wheel 10A corresponds to a portion (or region) of the grinding wheel 10 that overlaps a portion of the outer periphery of the wafer W in a crescent shape in a plan view. By arranging the grinding wheel 10 so that the grinding wheel 10A overlaps a portion of the outer periphery of the wafer W in a plan view (or so that the wafer W is accommodated inside and partially overlaps), the contact area can be made larger than, for example, grinding the outer periphery of the wafer W by contacting the outer periphery of the grinding wheel from the outside. For example, the area of ​​the grinding wheel 10A is preferably larger than the area of ​​the approximately elliptical shape where the grinding wheel 10 and the wafer W overlap in a plan view when the grinding wheel 10 is brought into contact with the wafer W from the outside. As shown in Figure 11, the grinding wheel 10 and the wafer W (adsorption table 4) are positioned so that the portion 10A1 of the grinding wheel 10A that intersects with the line passing through the rotation axis Ot and the rotation axis Ow is the target width of the trimming area of ​​the wafer W (hereinafter, sometimes referred to as the target trimming width).

[0078] 11, a nozzle NZ is provided so as to supply coolant (grinding fluid) near the contact start point (the portion where the outer periphery of the grinding wheel 10 and the wafer W first intersect in the rotation direction) between the grinding wheel 10 and the wafer W. Note that, although the nozzle NZ is shown to be provided on the outside of the grinding wheel 10 in FIG. 11, it may be provided on the inside of the grinding wheel 10 as long as it is possible to supply coolant near the contact start point between the grinding wheel 10 and the wafer W.

[0079] According to the processing apparatus 200 of the second embodiment, only a portion of the grinding wheel 10 contacts the wafer W, which further reduces heat generation during processing. Furthermore, according to the processing apparatus 200 of the second embodiment, coolant (grinding fluid) is more easily circulated at the processing point, improving processing efficiency and processing quality. Furthermore, poor lubrication of the abrasive grains of the grinding wheel 10 is less likely to occur, and the processing load is distributed, thereby improving the shape retention performance of the grinding wheel 10. As a result, processing quality can be stabilized and / or the grinding wheel life can be improved. Furthermore, while positioning accuracy is required when applying the grinding wheel to the outer peripheral edge of the wafer W from the outside, according to the processing apparatus 200 of the second embodiment, grinding can be performed simply by raising and lowering the grinding wheel 10 in the Z direction, eliminating the need for positioning accuracy and improving the processing quality of edge trimming of the wafer W.

[0080] (Embodiment 3) The processing apparatus 300 according to the third embodiment differs in configuration from the processing apparatuses of the above-described embodiments and modifications. The processing apparatus 300 according to the third embodiment is substantially the same as the processing apparatus 100 described above, except that the grinding wheel 1, the flange 2, and the grinding stone 10 each have a concentric multi-layer structure.

[0081] When bonding wafers W, it is preferable that the bonding strength between the two wafers W is uniform within the plane, but poor adhesion may cause unevenness in the bonding strength between the two wafers W. If unevenness occurs in the bonding strength between the two wafers W in this way, distortion such as unevenness or waviness may occur in the outer peripheral region of the wafers W.

[0082] Therefore, in some cases, the bonded wafer W is ground, including the bonding surface, to form a terrace so that the cross section of the outer end of the trimming area becomes L-shaped, thereby eliminating unevenness in the bonding strength of the bonded wafers W, and then a groove having a U-shaped cross section is machined on the inner periphery to remove the trimming area.

[0083] FIG. 12 is a partial cross-sectional view schematically showing a processing apparatus 300 according to the third embodiment. 12, the processing apparatus 300 grinds a bonded wafer W. The processing apparatus 300 may also grind a non-bonded wafer W.

[0084] The processing apparatus 300 includes, for example, a grinding wheel 1, a flange 2, a spindle 3, a suction table (or suction chuck) 4, a chuck spindle 5, a motor 6, a table motor (chuck motor) 7, a grinding wheel 10, and a controller (controller) 90. Note that the processing apparatus 100 may include components other than the grinding wheel 1, the flange 2, the spindle 3, the table (or chuck) 4, the chuck spindle 5, the motor 6, the table motor 7, the grinding wheel 10, and the controller (controller) 90.

[0085] In the third embodiment, the grinding wheel 1 has, for example, a concentric multi-layer structure. In the example shown in FIG. 12, the grinding wheel 1 has an inner grinding wheel 1i on the inner periphery side and an outer grinding wheel 1e on the outer periphery side. The inner grinding wheel 1i is provided inside the outer grinding wheel 1e so as to be vertically movable. The outer grinding wheel 1e may also be provided outside the inner grinding wheel 1i so as to be vertically movable.

[0086] In the third embodiment, the flange 2 has, for example, a concentric multi-layer structure. In the example shown in FIG. 12, the flange 2 has an inner flange 2i on the inner circumferential side and an outer flange e on the outer circumferential side. The inner flange 2i is provided inside the outer flange 2e so as to be vertically movable. The inner flange 2i is, for example, fitted into a hollow hole in the outer flange 2e. The outer flange 2e may also be provided outside the inner flange 2i so as to be vertically movable. The inner flange 2i and the outer flange 2e are attached so as to be rotatable in accordance with the rotation of the grinding wheel spindle 3. The inner flange 2i is attached to the grinding wheel spindle 3 so as to be vertically movable. The inner flange 2i and the outer flange 2e do not have to be connected to the grinding wheel spindle 3 as long as they are rotatable in accordance with the rotation of the grinding wheel spindle 3. The outer flange 2e may also be attached so as to be vertically movable to the grinding wheel spindle 3.

[0087] In the third embodiment, the grinding wheel 10 has, for example, a concentric multi-layer structure. In the example shown in FIG. 12, the grinding wheel 10 has an inner grinding wheel 10i on the inner periphery side and an outer grinding wheel 10e on the outer periphery side. The inner grinding wheel 10i is provided inside the outer grinding wheel 10e so as to be vertically movable. The radial width of the inner grinding wheel 10i (hereinafter referred to as the width of the inner grinding wheel 10i) is, for example, smaller than the radial width of the outer grinding wheel 10e (hereinafter referred to as the width of the outer grinding wheel 10e). Note that the outer grinding wheel 10e may be provided outside the inner grinding wheel 10i so as to be vertically movable. Furthermore, the width of the inner grinding wheel 10i may be, for example, equal to or greater than the width of the outer grinding wheel 10e.

[0088] The inner grinding stone 10i and the outer grinding stone 10e do not have to be perfectly circular as long as the segments constituting their respective layers are aligned on a predetermined circumference. The inner grinding stone 10i and the outer grinding stone 10e may each have a notch. The size of the notch is not particularly limited, and each layer may be a quarter-circular arc. In this case, the notch will be a three-quarters arc. Furthermore, since the inner grinding stone 10i has a small thickness, it does not have to be segmented. Furthermore, the grinding stone 10 may have two or more layers.

[0089] The inner grinding stone 10i and the outer grinding stone 10e process the trimming region of the bonded wafer W in two stages. For example, the outer grinding stone 10e cuts into and grinds the bonded wafer W from the upper substrate 20 to a part of the lower substrate 22, including the intermediate layer 21, so that the outer edge of the trimming region of the bonded wafer W has an L-shaped cross section. After the outer grinding stone 10e grinds the outer edge of the trimming region of the wafer W, the inner grinding stone 10i cuts into and grinds the bonded wafer W from the upper substrate 20 to a part of the lower substrate 22, including the intermediate layer 21, so that the trimming region of the bonded wafer W that is more inward than the trimming region ground by the outer grinding stone 10e has a U-shaped cross section.

[0090] The inner grinding wheel 1i is attached to the inner flange 2i and has an inner grinding wheel 10i on its underside. The inner grinding wheel 1i is circumferentially segmented on its underside. The outer grinding wheel 1e is attached to the outer flange 2e and has an outer grinding wheel 10e on its underside. The outer grinding wheel 1e is circumferentially segmented on its underside.

[0091] The inner grinding wheel 1i is rotated via the inner flange 2i by driving the motor 6. The outer grinding wheel 1e is rotated together with the inner grinding wheel 1i (outer flange 2e) via the outer flange 2e by driving the motor 6. In other words, the outer grinding wheel 1e and the inner grinding wheel 1i are rotated together by driving the motor 6.

[0092] FIG. 13 is a partial cross-sectional view schematically showing an example of grinding by the outer grindstone 10e of the processing device 300 according to the third embodiment. 13, an inner portion of the outer grinding stone 10e (or a part of the outer grinding stone 10e) faces the trimming region of the bonded wafer W. Note that the entire radial area of ​​the outer grinding stone 10e may face the trimming region of the bonded wafer W. The outer grinding stone 10e faces the outer end of the trimming region of the bonded wafer W, for example, so that the cross section of the outer end of the trimming region of the bonded wafer W becomes L-shaped when the bonded wafer W is ground.

[0093] The outer diameter of the outer grinding wheel 10e is slightly larger than the outer diameter of the bonded wafer W. The inner diameter of the outer grinding wheel 10e is approximately the same as the end face diameter of the ground bonded wafer. The inner diameter of the outer grinding wheel 10e is adjusted depending on the radial width of the terrace to be processed. In the example shown in FIG. 13, the outer diameter of the outer grinding wheel 10e is slightly larger than the outer diameter of the bonded wafer W, and the inner diameter of the outer grinding wheel 10e is slightly smaller than the outer diameter of the bonded wafer W.

[0094] 13, the rotation axis (or central axis) Ot of the outer grindstone 10e (outer grindstone wheel 1e, outer flange 2e, and / or grindstone spindle 3) and the rotation axis (or central axis) Ow of the bonded wafer W (suction table 4 and / or chuck spindle 5) coincide or approximately coincide. Note that the rotation axis of the outer grindstone 10e (outer grindstone wheel 1e, outer flange 2e, and / or grindstone spindle 3) and the rotation axis of the bonded wafer W (suction table 4 and / or chuck spindle 5) do not have to coincide (may be misaligned).

[0095] For example, the position (or arrangement) of the suction table 4 (or the bonded wafer W) and / or the outer grinding stone 10e (the outer grinding wheel 1e, the outer flange 2e, and / or the grinding stone spindle 3) may be adjusted by the controller 90 or the like so that the rotation axis Ow of the bonded wafer W and the rotation axis Ot of the outer grinding stone 10e (the outer grinding wheel 1e, the outer flange 2e, and / or the grinding stone spindle 3) substantially coincide with (are substantially coaxial with) each other. Note that if the positions of the suction table 4 (or the wafer W) and the outer grinding stone 10e (the outer grinding wheel 1e, the outer flange 2e, and / or the grinding stone spindle 3) are uniquely determined, it is not necessary to adjust these positions.

[0096] As shown in Figure 13, the outer grinding stone 10e (outer grinding wheel 1e and outer flange 2e) descends in the Z direction from the upper side of the bonded wafer W toward the surface (top surface) of the bonded wafer W (descending toward the tip of the arrow in Figure 13), cutting and grinding the outer end of the trimming area of ​​the wafer W so that the cross section is L-shaped.

[0097] The coolant (grinding fluid) is discharged toward the processing point where the outer grindstone 10e and the bonded wafer W come into contact with each other.

[0098] When the bonded wafer W is ground with the outer grindstone 10e, the inner grindstone 10i (the inner grindstone wheel 1i and the inner flange 2i) is positioned above the outer grindstone 10e (the outer grindstone wheel 1e or the outer flange 2e) so as not to come into contact with the wafer W. In other words, when the bonded wafer W is ground with the outer grindstone 10e, the lower surface of the inner grindstone 10i is positioned above the lower surface of the outer grindstone 10e at a distance equal to or greater than the thickness of the wafer W so as not to come into contact with the wafer W. Note that when the bonded wafer W is ground with the outer grindstone 10e, the lower surface of the inner grindstone 10i may be positioned above the lower surface of the outer grindstone 10e at a distance less than the thickness of the wafer W, as long as it is positioned so as not to come into contact with the wafer W. For example, when grinding the bonded wafer W with the outer grinding wheel 10e, the lower surface of the inner grinding wheel 10i may be positioned above the lower surface of the outer grinding wheel 10e at a distance equal to the depth of the desired groove to be formed in the trimming region of the wafer W so as not to come into contact with the wafer W.

[0099] The cutting speed of the outer grindstone 10e is adjusted in the same manner as in the embodiment 1. As shown in the embodiment 2, the outer grindstone 10e may be configured to come into contact with a part of the wafer W.

[0100] FIG. 14 is a partial cross-sectional view schematically illustrating an example of the processing device 300 at the end of grinding by the outer grindstone 10e according to the third embodiment. When the outer grindstone 10e forms a desired terrace at the outer end of the trimming region of the bonded wafer W, the processing device 300 ends grinding with the outer grindstone 10e. When grinding with the outer grindstone 10e ends, the outer grindstone 10e (and the inner grindstone 10i) moves upward from the bonded wafer W (toward the tip of the arrow in FIG. 14) in the Z direction as shown in FIG. 14, and returns to a predetermined position, for example, the initial position.

[0101] FIG. 15 is a partial cross-sectional view schematically illustrating an example of the processing apparatus 300 according to the third embodiment at the start of grinding by the inner grindstone 10i of the processing apparatus 300. As shown in FIG. After the trimming area of ​​the bonded wafer W is ground by the outer grinding wheel 10e, the inner grinding wheel 10i moves downward (toward the tip of the arrow in FIG. 15, or toward the bonded wafer W) relative to the outer grinding wheel 10e (outer grinding wheel 1e or outer flange 2e) from a predetermined position in the Z direction, for example, a position where it contacts the inner underside of the outer flange 2e, and is positioned at a predetermined position, for example, a position where it protrudes downward from the outer grinding wheel 10e and has the desired depth of the groove to be formed in the wafer W.

[0102] FIG. 16 is a partial cross-sectional view schematically showing an example of grinding by the inner grindstone 10i of the processing device 300 according to the third embodiment. In the example shown in FIG. 16 , the inner grindstone 10i faces a trimming region of the bonded wafer W that is located inside the groove ground by the outer grindstone 10e. The inner grindstone 10i is spaced apart from the outer grindstone 10e in the X direction so that the cross section of the trimming region of the bonded wafer W becomes U-shaped when the bonded wafer W is ground. Although the term “U-shaped” is used, the cross section does not necessarily have to be “U” shaped and may be well-shaped or V-shaped. In this specification, grooves having these cross-sectional shapes are also considered to be “U-shaped.” Furthermore, the inner grindstone 10i does not necessarily have to be spaced apart from the outer grindstone 10e in the X direction.

[0103] The outer diameter of the inner grinding stone 10i (the inner grinding wheel 1i and the inner flange 2i) is smaller than the outer diameters of the wafer W and the outer grinding stone 10e (the outer grinding wheel 1e and the outer flange 2e). The inner and outer diameters of the inner grinding stone 10i are adjusted according to the radial width of the groove formed in the trimming region of the wafer W.

[0104] 16, the rotation axis (or central axis) Ot of the inner grindstone 10i (inner grindstone wheel 1i, inner flange 2i, and / or grindstone spindle 3) and the rotation axis (or central axis) Ow of the bonded wafer W (suction table 4 and / or chuck spindle 5) coincide or approximately coincide. Note that the rotation axis of the inner grindstone 10i (inner grindstone wheel 1i, inner flange 2i, and / or grindstone spindle 3) and the rotation axis of the bonded wafer W (suction table 4 and / or chuck spindle 5) do not have to coincide (may be misaligned).

[0105] For example, the position (or arrangement) of the suction table 4 (or the bonded wafer W) and / or the inner grinding stone 10i (the inner grinding wheel 1i, the inner flange 2i, and / or the grinding stone spindle 3) may be adjusted by the controller 90 or the like so that the rotation axis Ow of the bonded wafer W and the rotation axis Ot of the inner grinding stone 10i (the inner grinding wheel 1i, the inner flange 2i, and / or the grinding stone spindle 3) substantially coincide (are substantially coaxial). Note that when the positions of the suction table 4 (or the wafer W) and the inner grinding stone 10i (the inner grinding wheel 1i, the inner flange 2i, and / or the grinding stone spindle 3) are uniquely determined, these positions do not need to be adjusted.

[0106] As shown in Figure 16, the inner grinding stone 10i (inner grinding wheel 1i and inner flange 2i) descends in the Z direction from above the bonded wafer W toward the surface (top surface) of the bonded wafer W that is inside the trimming area of ​​the bonded wafer W ground by the outer grinding stone 10e (descending toward the tip of the arrow in Figure 16), cutting into and grinding the trimming area of ​​the wafer W so that the cross section is U-shaped.

[0107] The coolant (grinding fluid) is discharged toward the processing point where the inner grindstone 10i and the bonded wafer W come into contact with each other.

[0108] When the bonded wafer W is ground with the inner grindstone 10i, the outer grindstone 10e (the outer grindstone wheel 1e and the outer flange 2e) is positioned above the inner grindstone 10i (the inner grindstone wheel 1i or the inner flange 2i) so as not to come into contact with the wafer W. In other words, when the bonded wafer W is ground with the inner grindstone 10i, the lower surface of the outer grindstone 10e is positioned above the lower surface of the inner grindstone 10i at a distance equal to or greater than the thickness of the wafer W so as not to come into contact with the wafer W. Note that when the bonded wafer W is ground with the inner grindstone 10i, the lower surface of the outer grindstone 10e may be positioned above the lower surface of the inner grindstone 10i at a distance less than the thickness of the wafer W, as long as it is positioned so as not to come into contact with the wafer W. For example, when grinding the bonded wafer W with the inner grinding wheel 10i, the lower surface of the outer grinding wheel 10e may be positioned above the lower surface of the inner grinding wheel 10i at a distance equal to the depth of the desired groove to be formed in the trimming region of the wafer W so as not to come into contact with the wafer W.

[0109] The cutting speed of the inner grindstone 10i is adjusted in the same manner as in the embodiment 1. As shown in the embodiment 2, the inner grindstone 10i may be configured to come into contact with a part of the wafer W.

[0110] FIG. 17 is a partial cross-sectional view schematically illustrating an example of the processing device 300 at the end of grinding by the inner grindstone 10i according to the third embodiment. When the inner grindstone 10i has formed a desired groove in the trimming region of the bonded wafer W, the processing device 300 ends grinding with the inner grindstone 10i. When grinding with the inner grindstone 10i is completed, the inner grindstone 10i moves upward from the bonded wafer W in the Z direction (toward the tip of the arrow in FIG. 17) as shown in FIG. 17, and returns to a predetermined position, for example, a position where it contacts the inner lower surface of the outer flange 2e.

[0111] As described above, the outer grinding wheel 10e forms an L-shaped terrace in the trimming area of ​​the wafer W, and the inner grinding wheel 10i forms a U-shaped groove in the trimming area of ​​the wafer W that is inward of the L-shaped terrace formed by the outer grinding wheel 10e, thereby removing the outer peripheral area of ​​the wafer W within the desired range (edge ​​trimming).

[0112] As described above, the processing apparatus 300 of embodiment 3 has an inner flange 2i that is movable up and down inside the outer flange 2e, so that it can easily perform full cutting of the wafer W, dual cutting, which achieves high throughput by performing full cutting or half cutting on two lines simultaneously, and step cutting, which performs cutting in two stages, half cutting and full cutting.

[0113] Furthermore, although the above description has been given of a configuration in which the outer and inner peripheries of the wafer W are processed separately, the inner flange 2i may be omitted and the inner grinding stone 10i and the outer grinding stone 10eB may be provided on the outer flange 2e with their bottom surfaces approximately aligned. In this case, it is possible to simultaneously form an L-shaped terrace at the outer end of the trimming region and form a U-shaped groove in the trimming region inward of the L-shaped terrace. It is preferable that the cross-sectional shapes of the layers of the concentric grinding stone 10 are different, but this shape is not limited to the above configuration.

[0114] FIG. 18 is a flowchart of edge trimming by the processing apparatus 300 according to the third embodiment. The controller 90 adjusts at least one of the positions of the grinding wheel 10 and the wafer W (suction table 4) (S10). The controller 90 rotates each of the grinding wheel 10 and the wafer W (suction table 4), and lowers the outer grinding wheel 10e while positioning the inner grinding wheel 10i so that it does not come into contact with the wafer W while the outer grinding wheel 10e is grinding the wafer W, thereby bringing the outer grinding wheel 10e into contact with the wafer W (S40).

[0115] When the outer grindstone 10e comes into contact with the trimming region of the wafer W, the controller 90 cuts into the wafer W by a predetermined amount in the thickness direction to grind it (S41).

[0116] When the desired groove has been formed in the trimming area of ​​the wafer W by the outer grinding wheel 10e, the controller 90 moves the outer grinding wheel 10e upward away from the wafer W, moves the inner grinding wheel 10i downwardly beyond the outer grinding wheel 10e, and positions the outer grinding wheel 10e so that it does not come into contact with the wafer W while the inner grinding wheel 10i is grinding the wafer W, and then lowers the inner grinding wheel 10i to bring the inner grinding wheel 10i into contact with the wafer W (S42).

[0117] When the inner grinding wheel 10i comes into contact with the trimming area of ​​the wafer W, the controller 90 cuts into the wafer W by a predetermined amount in the thickness direction to grind it (S43), moves the inner grinding wheel 10i upward from the wafer W, and ends the process.

[0118] According to the processing device 300 of the third embodiment, the above processing can be performed more quickly and easily.

[0119] (Embodiment 4) FIG. 19 is a partial cross-sectional view and a bottom view schematically showing a processing apparatus 400 according to the fourth embodiment. The processing device 400 is equipped with a ring-shaped piezoelectric element 50. The processing device 400 applies ultrasonic vibration to the grinding wheel 10 in the Z direction (thickness direction of the wafer W) using the ring-shaped piezoelectric element 50, and brings the grinding wheel 10 into contact with the trimming region of the wafer W, thereby grinding the trimming region (performing edge trimming).

[0120] The ring-shaped piezoelectric element 50 is annular and ring-shaped, and is built into the flange 2. There are no particular limitations on the size of the ring-shaped piezoelectric element 50, but in one form, the outermost periphery of the element is set to approximately the center position of the width (radial direction) of the grinding wheel 10, and the innermost periphery is set to be smaller than the inner diameter of the grinding wheel 10, and the element is attached biased toward the inner periphery of the grinding wheel 10.

[0121] The ring-shaped piezoelectric element 50 is supplied with power via a slip ring (not shown) that can withstand high rotation and is provided on the grinding wheel spindle 3, and ultrasonically vibrates in the vertical direction in the figure, i.e., in the Z direction. Note that ultrasonic waves are sound waves with a frequency of, for example, 20 kHz or higher, and the ring-shaped piezoelectric element 50 vibrates in the Z direction.

[0122] Here, the grindstone 10 is a general rigid body, and the flange 2 and grindstone wheel 1 are made of metal (iron or aluminum) as one form. Therefore, the ultrasonic vibration of the ring-shaped piezoelectric element 50 becomes vibration of the flange 2 and grindstone wheel 1, which results in movement (vibration) of the grindstone 10.

[0123] The grinding wheel 10 is segmented in the circumferential direction of the grinding wheel 1, that is, divided into multiple pieces, and notches 11 are provided between each of the segments to discharge coolant (grinding fluid) that cools the heat generated during processing, grinding chips, etc. Furthermore, ultrasonic vibrations are propagated to the grinding wheel 10 by the ring-shaped piezoelectric element 50, which causes a cavitation effect that makes it easier to introduce / discharge coolant and more easily discharge grinding chips, thereby suppressing clogging at the processing point.

[0124] Furthermore, the ring-shaped piezoelectric element 50 vibrates the grinding wheel 10 in the Z direction, which is the feed direction (removal direction), thereby improving grinding performance by adding to the original cutting ability and the vibration acceleration motion of the abrasive grains of the grinding wheel 10. Furthermore, because the ring-shaped piezoelectric element 50 is attached offset to the grinding wheel 10, the grinding resistance becomes a horizontal component force that is laterally directed relative to the cutting direction in the Z direction, thereby suppressing the pushing force during processing and reducing the bending load on the workpiece to be ground.

[0125] This allows for low-damage processing in the Z direction, and particularly suppresses cracking of the surface layer of the wafer W, peeling of the oxide film layer, and peeling of the bonding buffer layer, even in processing to form a terrace shape from the Z direction on the upper surface layer side of the bonded wafer W. This promotes cleaning of the grinding surface and discharge of grinding debris, and can maintain grinding performance and the accuracy of the grinding wheel shape.

[0126] FIG. 20 is a flowchart of edge trimming by the processing apparatus 400 according to the fourth embodiment.

[0127] The controller 90 executes the processes of S10 and S11 shown in FIG. 8, and executes the process of S20 shown in FIG. The controller 90 applies ultrasonic vibration to the grinding wheel 10 in the Z direction (central axis direction) using the ring-shaped piezoelectric element 50, and then cuts in and grinds the grinding wheel 10 by a predetermined amount (S30), and the process ends.

[0128] According to the processing apparatus 400 of embodiment 4, since it is equipped with a ring-shaped piezoelectric element 50, ultrasonic vibrations can be applied in the axial direction, which periodically releases the contact between the grinding wheel 10 and the wafer W, which facilitates the discharge of grinding chips and the like.

[0129] (Embodiment 5) FIG. 21 is a partial cross-sectional view and a bottom view schematically showing a processing apparatus 400 according to the fifth embodiment. The processing device 500 applies ultrasonic vibrations to the grinding wheel 10 in the Y direction (radial direction of the wafer W) using the ring-shaped piezoelectric element 51, brings the grinding wheel 10 into contact with the trimming area of ​​the wafer W, and grinds (edge ​​trims) the trimming area to form a terrace.

[0130] The ring-shaped piezoelectric element 51 is annular and ring-shaped, and is built into the flange 2. The ring-shaped piezoelectric element 51 is installed on the outer periphery of the flange 2, close to the inner periphery of the grinding wheel 1, above the grinding wheel 10, on the bottom side of the grinding wheel 1, and is attached offset in the thickness direction of the wafer W with respect to the grinding wheel 10. In other words, the ring-shaped piezoelectric element 51 is positioned above the contact position (processing point) between the grinding wheel 10 and the wafer W.

[0131] The ring-shaped piezoelectric element 51 is supplied with power via a slip ring (not shown) that can withstand high rotation and is provided on the grinding wheel spindle 3, and ultrasonically vibrates in the radial direction, i.e., the Y direction, in the figure. Therefore, the ultrasonic vibration of the ring-shaped piezoelectric element 51 strikes the wafer W approximately parallel to the upper surface of the grinding wheel 10, and as it goes further downwards on the grinding wheel 10, the moment from the ring-shaped piezoelectric element 51 increases, causing the vibration direction to tilt vertically.

[0132] Therefore, the deeper the machining point between the grinding wheel 10 and the wafer W, the larger the amplitude of the ultrasonic vibration becomes, and the same is true for the gap, making it easier for coolant to enter and cavitation to occur. This promotes the inflow and outflow of coolant, promotes cleaning of the grinding surface, promotes the discharge of grinding debris, ensures a stable protrusion amount of the grinding abrasive grains, and improves processing quality.

[0133] Furthermore, the ring-shaped piezoelectric element 51 applies ultrasonic vibrations to the grinding wheel 10 in the Y direction, which enhances the grinding performance by adding vibration acceleration motion of the abrasive grains to the original cutting ability. This allows for low-damage processing, and in the case of a bonded wafer W, even if one of the upper substrate 20 or the lower substrate 22 is made of a highly brittle material that has a large grinding resistance, is easily deformed, and is prone to peeling from the bonded wafer, it is possible to simultaneously remove and process the upper substrate 20 and the lower substrate 22 on the bonded device side.

[0134] Furthermore, the ring-shaped piezoelectric element 51 vibrates the abrasive grains in the Y direction, which increases the mobility of the abrasive grains and improves the processing efficiency, enabling processing speeds faster than normal processing speeds.In addition, by preventing clogging and improving processing performance, shape accuracy and grinding wheel life can be improved.

[0135] The flowchart of edge trimming by the processing device of the fifth embodiment is the same as the flowchart shown in FIG. 19 of the fourth embodiment, except that the direction of the ultrasonic vibration is different.

[0136] According to the processing apparatus 500 of the fifth embodiment, the same effects as those of the fourth embodiment can be obtained.

[0137] The machining apparatus of each of the above-described embodiments includes a controller (not shown). The controller is a computer including a processor and a memory, and each unit is controlled by a program pre-stored in the controller, so that a predetermined machining method can be performed. [Explanation of symbols]

[0138] 1...Grinding wheel 1i...Inner grinding wheel 1e...Outer grinding wheel 2...Flange 2i...Inner flange 2e...Outer flange 3...Grinding wheel spindle 4...Suction table 5...Chuck spindle 6...Motor 7...Table motor 10...Grinding stone 10i...Inner grinding stone 10e…Outer grindstone 11...Notch 20...Upper board 21...Middle class 22...Lower board 50...Ring-type piezoelectric element 51...Ring-type piezoelectric element Ot...Central axis (rotation axis) Ow...Central axis (rotation axis) W...Wafer (bonded wafer)

Claims

1. A processing method in which a grinding wheel facing the outer peripheral region of a wafer is brought into contact with the wafer contained in an area surrounded by the grinding wheel in a planar view, and the grinding wheel cuts into the wafer in the thickness direction to grind and remove the outer peripheral region.

2. 2. The processing method according to claim 1, wherein the grinding wheel is brought into contact with the wafer parallel to the surface of the wafer, and the grinding wheel cuts into the wafer in a thickness direction to grind the wafer.

3. The grinding wheel has an outer diameter larger than the diameter of the wafer and an inner diameter smaller than the diameter of the wafer, The processing method according to claim 1 , wherein the grinding wheel is disposed relative to the wafer so that a central axis of the grinding wheel and a central axis of the wafer coincide with each other.

4. The inner diameter of the grinding wheel is larger than the diameter of the wafer, The processing method according to claim 1 , wherein the grinding wheel is used to cut into the wafer in a thickness direction so that only a portion of the grinding wheel comes into contact with the outer peripheral region.

5. The processing method according to claim 1 , wherein the grinding wheel has at least one notch in the circumferential direction.

6. The contacting and the grinding may include the following steps: bringing the grinding wheel closer to the wafer from the direction in which the surface faces; cutting in the thickness direction at a first speed when the grinding wheel contacts the surface; After a predetermined amount of cutting has been performed at the first speed, the cutting speed is switched to a second speed, The processing method according to claim 1 , wherein the second speed is greater than the first speed.

7. The processing method according to claim 1 , wherein the grinding is performed by separating the grindstone and the wafer periodically or non-periodically.

8. The processing method according to claim 7 , wherein the separation is performed by applying ultrasonic vibration to at least one of the grindstone and the wafer.

9. The processing method according to claim 1 , wherein the grinding wheel has a concentric multi-layer structure.

10. The processing method according to claim 9 , wherein each layer constituting the multilayer structure is brought into contact with the other layer independently to form cuts having different cross-sectional shapes in the wafer.

11. A processing apparatus for removing an outer peripheral region from a wafer, a holder for holding the wafer; a grindstone facing the outer peripheral region of the wafer; a rotation mechanism that rotates at least one selected from the group consisting of the grinding wheel and the wafer in a circumferential direction, The processing device, in which the wafer is accommodated in an area surrounded by the grindstone when viewed in a plane.

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